This invention concerns gas turbine engines of a type that can be especially useful for driving electric generators or vehicles and in other applications where it is preferred to have a moderate power output, small size and high response speed. A gas turbine engine of this type has a compressor, a combustor mounted downstream of the compressor and a power turbine mounted downstream of the combustor.
A compressor turbine, rotating in a direction opposite to the direction of rotation of the power turbine, is mounted downstream of the power turbine for driving the compressor. The engine has a temperature control system for controlling the temperature at the outlet of said compressor turbine, as referred to in a pending application Ser. No. 09/267,893. The compressor in this gas turbine engine rotates independently of the power turbine and compresses gas from the compressor turbine exhaust to feed this gas back to the combustor and through a heat exchanger for power turbine cooling, as described in detail in our earlier patent application Ser. No. 09/161,115.
When the gas turbine engine idles, the compressor must continue to rotate and sustain recirculation of the exhaust gas in the flow duct of the engine because otherwise combustion in the combustor cannot be sustained, and the engine will not be able to sustain the load when the load is again applied. In order to rotate the compressor in the no-load mode (when the power turbine does not rotate and the compression ratio in the compressor substantially decreases), the efficiency is very low, and too much fuel is consumed without doing any useful work. In addition, burning too much fuel without generating power is associated with useless harmful emissions (both thermal and chemical). This gas turbine engine, while having a very good efficiency over the major part of the power range, is rather inefficient when it idles, similarly to the majority of the state-of-the art thermal engines.
This disadvantage is eliminated in the gas turbine engine according to the invention as described below.
It is an object of the invention to provide a gas turbine engine in which the fuel consumption is minimized or eliminated when the engine idles.
Another object of the invention is to improve the overall fuel economy of the gas turbine engine of the above-described type.
A further object of the invention is to reduce harmful emissions of the gas turbine engine when the engine idles.
The foregoing objects are accomplished by a gas turbine engine having a compressor, a combustor mounted downstream of the compressor, and a power turbine mounted downstream of the combustor. This engine has a compressor turbine that is mounted downstream of the power turbine for producing power to drive the compressor and that rotates in a direction opposite to the direction of rotation of the power turbine. The gas turbine engine has a temperature control system for keeping a preset temperature at the compressor turbine outlet, a fuel supply control system, a drive motor to drive the compressor rotation, a motor control system having a motor power-up module with an input connected to the fuel supply control system and a motor power output control module with a first input connected to the motor power-up module and an output which is connected to the drive motor, and a temperature sensor positioned at the outlet of the compressor turbine and connected to a second input of the motor power output control module.
Other objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof and the accompanying drawings.